Common motor analyses focus on geometric parameters and use assumptions to remove number of coil turns, \(n_t\) , from consideration [1]}, [2]}.
However, \(n_t\)  is a useful “lever” for motor designers to use in manipulating motor properties [3]}.
The parameter \(n_t\)  is linearly related to the shear force generated between the stator and rotor in the motor, as it amplifies the magnetic field of the motor coil.
Thus, \(K_T \propto n_t\) .
In the case of the U8 motor, \(n_t \approx 16\)  and for the RI50, \(n_t \approx 36\)  by visual inspection.
This greater \(n_t\)  allows the RI50 motor to partially make up for its radius disadvantage with respect to \(K_T\) , and also explains the higher \(R_\phi \)  and \(L_e\)  for the RI50.
This effect is captured by the \(S_T\)  metric (REF ), and is also discussed in [4]}.
